North Korea's state media have harshly criticized South Korean President Yoon Suk Yeol over his warning about Pyongyang's arms deals with Moscow.
A commentary carried by the KCNA news agency on Monday accused Yoon of acting as a "loudspeaker for the US" and talking viciously about North Korean and Russian relations.
"It is self-evident that such a guy with a trash-like head cannot understand the profound and enormous meaning of the development of the DPRK-Russia friendly relations," the commentary said.
A spokesman for the Unification Ministry in Seoul condemned the remarks as vulgar and said they were not worthy of a response from South Korea.
Yoon had said last week in his speech to the UN General Assembly in New York that any arms deal between North Korea and Russia would be seen as a "direct provocation." South Korea, its allies and partners would not stand idly by.
The US and South Korea have recently expressed concern several times about North Korean dictator Kim Jong Un's negotiations with Russian President Vladimir Putin in Russia earlier this month. Putin spoke of there being potential for expanding military cooperation.
Experts say North Korea could supply artillery ammunition and missiles for Russia's war against Ukraine. In return, a transfer of modern Russian military technologies is said to be under discussion.
North Korea, which is largely isolated, is subject to international sanctions because of its nuclear weapons and missile programme.
